The present invention relates to a spindle motor using a hydraulic bearing, for example, adapted to a large volume disk drive such as a removable hard disk drive, and to a disk drive on which such a spindle motor is mounted.
In disk drives such as removable-hard disk drives (hereinafter, referred to as xe2x80x9cR-HDDsxe2x80x9d), information has been recorded and/or reproduced by removably mounting an information recording disk such as a hard disk, which has been previously contained in a removable-hard disk cartridge (hereinafter, referred to as xe2x80x9cR-HDCxe2x80x9d), to a spindle motor, rotating the disk at a high speed by the spindle motor to generate an air flow on a surface of the disk, and flying a flying head slider supported on a leading end of a head actuator via a suspension over a surface of the disk, thereby seeking recording tracks on the disk.
A spindle motor 101 using a hydraulic bearing shown in FIG. 17 is used for R-HDDs of this type.
The configuration of the spindle motor 101 will be described below. An approximately cruciform hydraulic bearing 103 is formed in an approximately central portion of a motor base 102. A spindle 104 has a lower end 104a and a rotating disk portion 105 fixed to or formed integrally with an outer periphery of an approximately intermediate portion of the spindle 104 in the axial direction. The lower end 104a of the spindle 104 and the rotating disk portion 105 are floated in oil 106 that is a fluid previously put to fill the hydraulic bearing 103. Upper and lower portions of the hydraulic bearing 103 are sealed with an upper plate 107 and a lower plate 108 fixed to upper and lower portions of the motor base 102, respectively. An inner wall surface 103a, on the motor base 102 side, of the hydraulic bearing 103 is separated from each of an outer peripheral surface of the lower end 104a and an outer surface of the rotating disk portion 105 with a fine gap put therebetween. The outer peripheral surface of the lower end 104a of the spindle 104 has a plurality of annular grooves 109, and also each of the upper and lower sides of the outer surface of the rotating disk portion 105 has a plurality of annular grooves 110. Because of the action of a dynamic pressure of the oil 106 caused in these annular grooves 109 and 110, the spindle 104 and the rotating disk portion 105 are integrally rotated in a state being floated on the oil 106, that is, in a state being not in contact with the inner wall surface 103a of the hydraulic bearing 103.
A rotor 111 is fixed to a portion, near an upper end 104b, of the spindle 104. A disk table 112, to which a hard disk or the like is to be exchangeably mounted, is formed on a central portion of the upper end of the rotor 111. An annular magnet 113 is fixed to an inner periphery of the lower end of the rotor 111. A stator 116, which is composed of a stack 114 of silicon steel plates and a plurality of coils 115 wound around the stack 114, is mounted at a portion between the outer periphery of the hydraulic bearing 103 of the motor base 102 and the inner periphery of the magnet 113.
A rotational force is generated between the plurality of coils 115 and the magnet 113 by switching the supply of a current to the coils 115, whereby the rotor 111 is rotated, together with the spindle 104 and the rotating disk portion 105, with respect to the motor base 102. The spindle motor 101 having the above configuration functions as a flat brushless motor.
The related art spindle motor 101 using the hydraulic bearing 103, however, has a disadvantage. In this spindle motor 101, each of a pair of upper and lower corners of the outer periphery of the rotating disk portion 105 is formed as a sharp edge 105a. By the way, a moment stronger than a dynamic pressure caused in the hydraulic bearing 103 is generated due to external vibration/impact and the like applied during operations of recording and/or reproducing information on and/or from a hard disk or the like. Consequently, as shown in FIG. 18, when an axis P2 of the spindle 104 is tilted in the hydraulic bearing 103 with respect to a vertical reference P1 of the motor base 102 at a specific angle xcex81, the sharp edges 105a of the outer periphery of the rotating disk portion 105 may be often brought into contact with the inner wall surface 103a, particularly, of the upper plate 107 of the hydraulic bearing 103.
The frictional force caused by such contact acts as a braking force against rotation of the rotor 111, to cause a variation in rotational speed of the rotor 111, thereby failing to stably record and/or reproduce information on and/or from a hard disk or the like.
An object of the present invention is to provide a spindle motor using a hydraulic bearing, which is capable of preventing a variation in rotational speed of the spindle motor as much as possible, which variation is caused by tilting of the axis of the spindle motor due to external vibration/impact and the like, and to provide a disk drive using such a spindle motor.
To achieve the above object, according to a first aspect of the present invention, there is provided a spindle motor including a spindle; a rotating disk portion rotatable integrally with the spindle; and a hydraulic bearing, formed in a motor base, for rotatably supporting the rotating disk portion; wherein an escape portion is provided for preventing the rotating disk portion from being brought into contact with an inner wall surface of the hydraulic bearing when the spindle is tilted with respect to the motor base at a specific angle or less.
The escape portion is preferably configured as an R-face or a C-face formed at an edge of an outer periphery of the rotating disk portion.
The escape portion is preferably configured as a recess formed in the inner wall surface of the hydraulic bearing at a position facing to an edge of an outer periphery of the rotating disk portion.
A region, to be brought into contact with the inner wall surface of the hydraulic bearing when the spindle is tilted with respect to the motor base at an angle more than the specific angle, of the rotating disk portion is preferably formed into a mirror-finished surface having a surface roughness of 0.3 s or less in Ra.
A region, to be brought into contact with the rotating disk portion when the spindle is tilted with respect to the motor base at an angle more than the specific angle, of the inner wall surface of the hydraulic bearing is formed into a mirror-finished surface having a surface roughness of 0.3 s or less in Ra.
To achieve the above object, according to a second aspect of the present invention, there is provided a disk drive including a spindle motor including a spindle, a rotating disk portion rotatable integrally with the spindle, and a hydraulic bearing, formed in a motor base, for rotatably supporting the rotating disk portion, the disk drive being operated to rotate an information recording disk by the spindle motor, thereby recording and/or reproducing information on and/or from the disk by a flying head slider; wherein an escape portion is provided for preventing the rotating disk portion from being brought into contact with an inner wall surface of the hydraulic bearing when the spindle is tilted with respect to the motor base at a specific angle or less.
To achieve the above object, according to a third aspect of the present invention, there is provided a hydraulic bearing structure including a hydraulic bearing, formed in a motor base, for rotatably supporting a rotating disk portion rotatable integrally with a spindle; wherein an escape portion is provided for preventing the rotating disk portion from being brought into contact with an inner wall surface of the hydraulic bearing when the spindle is tilted with respect to the motor base at a specific angle or less.
With the configuration of the spindle motor using a hydraulic bearing according to the first aspect of the present invention, since an escape portion is provided for preventing the rotating disk portion rotating in the hydraulic bearing together with the spindle from being brought into contact with an inner wall surface of the hydraulic bearing when the spindle is tilted with respect to the motor base at a specific angle or less, the contact of the rotating disk portion with the inner wall surface of the hydraulic bearing due to external vibration/impact and the like applied during rotation of the spindle motor can be prevented as much as possible.
The above escape portion for preventing the rotating disk portion from being brought into contact with the inner wall surface of the hydraulic bearing by tilting of the spindle with respect to the motor base can be configured as an R-face or C-face formed at an edge of the outer periphery of the rotating disk portion or a recess formed in the inner wall surface of the hydraulic bearing so as to face to the edge of the outer periphery of the rotating disk portion.
A region, to be brought into contact with the inner wall surface of the hydraulic bearing when the spindle is tilted with respect to the motor base at an angle more than the specific angle, or a region, to be brought into contact with the rotating disk portion when the spindle is tilted with respect to the motor base at an angle more than the specific angle, of the inner wall surface of the hydraulic bearing, can be formed into a mirror-finished surface having a surface roughness of 0.3 s or less in Ra.
With the configuration of the disk drive according to the second aspect of the present invention, an escape portion is provided for preventing the rotating disk portion rotating in the hydraulic bearing together with the spindle from being brought into contact with the inner wall surface of the hydraulic bearing when the spindle is tilted with respect to the motor base at a specific angle or less during operation of the disk drive for rotating an information recording disk by the spindle motor using the hydraulic bearing, thereby recording and/or reproducing information on and/or from the disk by the flying head slider. As a result, the contact of the rotating disk portion with the inner wall surface of the hydraulic bearing due to external vibration/impact and the like applied during operations of recording and/or reproducing information on and/or from the disk can be prevented as much as possible.
With the configuration of the hydraulic bearing structure according to the third aspect of the present invention, an escape portion is provided for preventing, even if the hydraulic bearing structure is used for not only a spindle motor but also a general motor, the rotating disk portion rotating in the hydraulic bearing together with the spindle from being brought into contact with an inner wall surface of the hydraulic bearing when the spindle is tilted with respect to the motor base at a specific angle or less. As a result, the contact of the rotating disk portion with the inner wall surface of the hydraulic bearing due to external vibration/impact and the like can be prevented as much as possible.